The overall goal of this project is to improve the results of tendon repair through the development of therapies that affect the tendon gliding surface. In the first two funding periods we showed that surgeons could reduce adhesions after tendon repair by changes in suture methods and postoperative therapy regimens. These changes have been incorporated into clinical practice in our own and other centers. In the third funding period, we explored means to further improve tendon gliding and reduce adhesions by physicochemical and pharmacological means. These studies have shown that adhesions can be dramatically reduced with an engineered tendon surface coating containing lubricin, a lubricating glycoprotein ubiquitous in articular cartilage, but in some cases the healing process in lubricin treated tendons is delayed. In this funding period, therefore, we propose to investigate methods to preserve the beneficial effects of lubricin while improving intrinsic tendon healing through a tissue engineering approach. We have recently developed an interpositional collagen patch seeded with bone marrow-derived stromal cells (BMSC) that appears to accelerate tendon healing in vitro. Our central hypothesis is that this BMSC seeded patch will improve the speed and strength of tendon healing in vivo, without adversely affecting the beneficial effects of lubricin-augmented repair and rehabilitation on tendon gliding and adhesions. To test this hypothesis we have developed three aims. Aim 1 is to investigate the healing of flexor tendons following the incorporation of BMSC seeded, cytokine augmented collagen patch into the repair site in a canine model in vitro. Aim 2 is to investigate the effects a BMSC tendon patch combined with surface modification on flexor tendon repair in a canine model in vivo. Aim 3 is to investigate the effect of surface modification and a BMSC patch on animals subjected to a postponed tendon rehabilitation protocol. If these aims are achieved, we believe that this two-pronged tissue engineering approach could be developed into a clinical method to provide sound, adhesion free tendon repairs. In addition, such an approach could provide benefits in reducing adhesions in clinical situations where immediate rehabilitation with early motion is impossible, such as in cases of replantation or other complex trauma, as well as in young children or other uncooperative patients.